JP2005350652A - Lubricant, magnetic recording medium and method for producing magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant, particularly a lubricant for magnetic recording medium in which excellent lubricating ability is kept under various use conditions and lubricating effect is retained even in long-time use. <P>SOLUTION: The lubricant is obtained by mixing at least one compound selected from compounds represented by general formula (a) (wherein R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are each hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group and at least either one of R<SP>1</SP>and R<SP>2</SP>is hydrogen and at least either one of R<SP>3</SP>and R<SP>4</SP>is hydrogen; m is an integer of 1-6 and n is an integer of 1-5 and p and q are each an integer of 0-30 and r is an integer of 1-12) with at least one compound selected from compounds represented by general formula (b) (wherein R<SP>5</SP>and R<SP>6</SP>are each an aliphatic alkyl group or an aliphatic alkenyl group; x is an integer of 1-6 and y is an integer of 1-5 and s and t are each an integer of 0-30 and u is an integer of 1-12) and general formula (c) (wherein R<SP>7</SP>is a fluoroalkyl group, a fluoroalkenyl group, a fluoroether group or a fluoropolyether and R<SP>8</SP>is an aliphatic alkyl group or an aliphatic alkenyl group and a is an integer of 1-12) and preferably further mixing the mixture with a compound represented by general formula (d) (wherein R<SP>9</SP>and R<SP>10</SP>are each hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group; b is an integer of 1-12; v is an integer of 1-12; w is an integer of 1-6; z is an integer of 1-5; h and k are each an integer of 0-30). The lubricant is used to form a lubricant layer of a magnetic recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lubricant used for precision machines or precision parts that require highly accurate lubricity, a magnetic recording medium using the lubricant, and a method of manufacturing the magnetic recording medium.

  In recent years, in the field of magnetic recording, high-performance magnetic recording media suitable for it have been actively developed along with digital recording / reproducing equipment with higher performance such as downsizing and longer usage time. Yes. Recently, a metal thin film type magnetic recording medium, which is extremely advantageous for short wavelength recording, has been put into practical use in place of a coating type magnetic recording medium. In general, a metal thin film type magnetic recording medium refers to a tape, a disk, or the like in which a magnetic layer made of a ferromagnetic metal thin film is provided as a recording layer on a nonmagnetic support. Further, examples of the magnetic recording medium system used for recording / reproducing of the high-density magnetic recording medium include a digital video deck and a hard disk drive.

  In a metal thin film type magnetic recording medium represented by digital video tape, the magnetic layer has a very good surface property, that is, the roughness of the surface of the magnetic layer is small. For this reason, the contact area between the magnetic layer and the magnetic head increases, so that the magnetic layer is easily worn by receiving a large frictional force during high-speed sliding with the magnetic head in the signal recording / reproducing process. The wear of the magnetic layer greatly affects the running durability or the still durability of the magnetic recording medium. Therefore, reducing it is a major issue in the research and development of metal thin film magnetic recording media.

  Therefore, attempts have been made to reduce wear and improve running durability and still durability by providing a protective film and a lubricant layer in this order on the surface of the magnetic layer. When providing a lubricant layer, the protective layer and lubricant layer provided on the surface of the magnetic layer should be thin so as to increase output by minimizing the decrease in output due to spacing loss between the magnetic recording medium and the magnetic head. Is required. In particular, the lubricant layer is required to exhibit lubricating properties with a thickness of only a few nm.

  A general hard disk drive employs a CSS (contact start / stop) system. In the CSS system, when the hard disk, which is a high-density magnetic recording medium, is stopped, the magnetic head comes into contact with the disk, and when the hard disk starts rotating at startup, the magnetic head is It is a system that floats from the surface of the disk and performs recording / reproduction in this state. Then, the rotation of the disk is decelerated when stopped, and the magnetic head comes into contact with the hard disk again.

  In this CSS system, the magnetic head rubs against the surface of the hard disk when the disk is stopped or started, so the frictional force applied at that time is a big problem. In order to maintain the reliability of the hard disk drive, it is desirable that the friction coefficient of the medium after the CSS running test is the same as the initial one. However, it is difficult to satisfy this requirement with a magnetic disk with high surface flatness, that is, with a low roughness. In addition, a so-called head crash, in which the head and the medium collide when the hard disk rotates at a high speed, is one of the problems to be solved. One of the factors that cause the head crash is that the magnetic recording medium does not have an appropriate protective film and lubricant layer.

  Therefore, lubricants suitable for magnetic recording media have been widely studied. One of them is a fluorine compound. Since fluorine-based compounds exhibit excellent lubricating properties, use of various fluorine-based compounds has been proposed (Patent Documents 1 to 4).

  However, with the further increase in recording density, it is necessary to consider measures for new technologies such as mounting of MR heads or GMR heads and adoption of contact recording methods. For this purpose, it is necessary to further improve the characteristics of the lubricant used in the magnetic recording medium.

JP 2002-92858 A JP 2002-150530 A JP 2002-241349 A JP-A-5-194970

  The characteristics required for lubricants used in magnetic recording media are excellent in lubrication characteristics even when used in low-temperature environments, can be applied very thinly while maintaining lubrication characteristics, and maintain lubrication characteristics even after long-term use. In addition, it is required that there is little powder on the magnetic head. Here, “with powder” means that the lubricant is scraped from the magnetic recording medium by contact with the magnetic head during traveling in the magnetic recording / reproducing apparatus, and the scraped powder is accumulated in the magnetic head.

However, the characteristics required for the lubricant are required to be very severe in terms of the characteristics of the magnetic recording medium. Therefore, it is difficult to satisfy all of these requirements with a conventionally used lubricant.

  The present invention has been made in view of the above circumstances, and while maintaining excellent lubricity under various use conditions, the lubrication effect is maintained even after long-term use, and a lubricant layer of a magnetic recording medium is formed. In this case, it is an object to provide a lubricant that gives a magnetic recording medium with less dust, a magnetic recording medium using the lubricant, and a method for manufacturing the same.

（式中、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４はそれぞれ水素、脂肪族アルキル基または脂肪族アルケニル基を示し、Ｒ^１およびＲ^２の少なくとも一方が水素であり、Ｒ^３およびＲ^４の少なくとも一方が水素であり、ｍは１から６の整数であり、ｎは１から５の整数であり、ｐ、ｑはそれぞれ０から３０の整数であり、ｒは１〜１２の整数である。）

（式中、Ｒ^５、Ｒ^６は、脂肪族アルキル基または脂肪族アルケニル基を示し、ｘは１から６の整数であり、ｙは１から５の整数であり、ｓ、ｔはそれぞれ０から３０の整数であり、ｕは１〜１２の整数である。）

（式中、Ｒ^７はフルオロアルキル基、フルオロアルケニル基、フルオロエーテル基もしくはフルオロポリエーテル基を示し、Ｒ^８は脂肪族アルキル基または脂肪族アルケニル基を示し、ａは１〜１２の整数である。） In order to solve the above problems, the present invention provides, in the first aspect, a lubricant having a specific composition. Such a lubricant includes at least one compound selected from fluorine-based diester dicarboxylic acid compounds represented by the following general formula (a), a fluorine-based diester compound represented by the following general formula (b), and the following general formula (c). At least one compound selected from fluorine-based monoester compounds represented by the formula:

^(Wherein, R ^1, R ^2, R 3, ^{R 4} each represent hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group, at least one of ^{R 1} and ^{R 2} are hydrogen, ^{R 3} and ^{R 4} At least one is hydrogen, m is an integer from 1 to 6, n is an integer from 1 to 5, p and q are each an integer from 0 to 30, and r is an integer from 1 to 12. )

(Wherein R ⁵ and R ⁶ represent an aliphatic alkyl group or an aliphatic alkenyl group, x is an integer of 1 to 6, y is an integer of 1 to 5, and s and t are each from 0 to 6) 30 is an integer, and u is an integer of 1 to 12.)

(In the formula, R ⁷ represents a fluoroalkyl group, a fluoroalkenyl group, a fluoroether group or a fluoropolyether group, R ⁸ represents an aliphatic alkyl group or an aliphatic alkenyl group, and a is an integer of 1 to 12. .)

  The lubricant of the present invention is characterized in that the compound represented by the general formula (a) is combined with the general formula (b) and / or the general formula (c). When a lubricant layer of a magnetic recording medium is formed using a lubricant composed of this specific combination of compounds, a magnetic recording medium having excellent running durability and still characteristics can be obtained.

（式中、Ｒ^９、Ｒ^１０はそれぞれ水素、脂肪族アルキル基または脂肪族アルケニル基を示し、ｂは１〜１２の整数であり、ｖは１〜１２の整数であり、ｗは１〜６の整数であり、ｚは１〜５の整数であり、ｈおよびｋはそれぞれ０〜３０の整数である。） The lubricant of the present invention is preferably a combination of the compound represented by the general formula (a) with the general formula (b) and / or the general formula (c), and further represented by the following general formula (d). Are provided in combination. When the lubricant layer of the magnetic recording medium is formed using this lubricant by adding the compound represented by the general formula (d), a magnetic recording medium having further excellent running durability can be obtained.

(In formula, R <^9> , R < ¹⁰ > shows hydrogen, an aliphatic alkyl group, or an aliphatic alkenyl group, respectively, b is an integer of 1-12, v is an integer of 1-12, w is 1-6. Z is an integer of 1 to 5, and h and k are each an integer of 0 to 30.)

  The reason why good performance can be achieved when the lubricant layer of the magnetic recording medium is formed with the lubricant of the present invention is considered as follows, but this does not restrict the present invention at all. First, in all the compounds represented by the general formulas (a) to (c), the ester bond R ″ COOR ′ has a fluorine atom in the R ′ of the alkoxyl group —OR ′ and the R ″ of the acyl group R ″ CO—. In the lubricant of the present invention, the acyl group does not have a fluorine-containing group such as a fluoroalkyl group in the compound contained as a main component, that is, an aliphatic alkyl group or an aliphatic alkenyl group. Further, since the compound represented by the general formula (a) has a carboxyl group at the terminal, it contributes to the improvement in running durability of the magnetic recording medium, and the general formula ( Since the compounds represented by b) and (c) contain an ester bond at the terminal, they contribute to an improvement in the still life of the magnetic recording medium and reduce head dusting. In the magnetic recording medium, good running durability and still life, and less dusting can be achieved at the same time, and the compound represented by the general formula (b) is a compound represented by the general formula (a). Similarly, since the compound has a fluoroether group in the molecule, the compound represented by the general formula (b) and the compound represented by the general formula (a) have high compatibility, and therefore are represented by the general formula (a). By combining the compound and the compound represented by the general formula (b), a lubricant having excellent uniformity can be obtained.The compound represented by the general formula (b) also has the number of ester bonds in one molecule. The compound represented by the general formula (c) has a smaller number of ester bonds but a smaller molecular weight than the compound represented by the general formula (b). Since the molecular volume is small, it contributes to the improvement of the runnability of the magnetic recording medium, so that the combination of the compound represented by the general formula (a) and the compound represented by the general formula (c) Driving characteristics can be kept stable.

  The compound represented by the general formula (d) has a fluoroalkyl ether chain as a main chain, each of which has nitrogen, the nitrogen atom is bonded to one hydroxyalkyl group, and hydrogen, an aliphatic alkyl group Alternatively, it has a structure bonded to either an aliphatic alkenyl group. In the compound represented by the general formula (d), the hydroxyalkyl group bonded to both nitrogen atoms is considered to play a role of improving the adhesion of the lubricant to the object (for example, a protective film of a magnetic recording medium). It is done. The compound represented by the general formula (d) is characterized in that one hydroxyalkyl group is bonded to each nitrogen atom and is limited to two in one molecule. Due to this feature, the compound represented by the general formula (d) is excessively adsorbed on a counterpart object (for example, a magnetic head of a magnetic recording / reproducing apparatus) in sliding contact with an object applied as a lubricant. Accordingly, it is possible to prevent the lubrication characteristics of the object from being deteriorated, and it is possible to prevent the lubricant adsorbed on the other object (for example, the magnetic head) from aggregating to generate a powdery material. Further, when an aliphatic alkyl group or an aliphatic alkenyl group is bonded to at least one nitrogen atom, these groups are considered to particularly contribute to the improvement of the lubricating properties. Therefore, in addition to the high adhesion provided by nitrogen atoms and the lubrication properties provided by fluoroalkyl ether chains, this compound exhibits excellent properties for the groups bonded to the nitrogen atoms. It is assumed that it functions as a balanced lubricant.

  In the second aspect, the present invention provides a ferromagnetic metal film formed as a magnetic layer on a nonmagnetic support, a protective film formed on the magnetic layer, and a lubricant layer formed on the protective film. A magnetic recording medium having a lubricant layer containing at least one lubricant of the present invention is provided. The magnetic recording medium of the present invention has excellent still characteristics and running durability because the lubricant layer is a layer comprising the lubricant of the present invention.

  In the third aspect, the present invention also provides a method for producing the magnetic recording medium of the present invention. The method for producing a magnetic recording medium of the present invention is characterized by the lubricant layer forming step, and the other steps may be steps conventionally used for producing a magnetic recording medium. The formation process of the lubricant layer in the production method of the present invention includes a coating solution prepared by dissolving a compound constituting the lubricant layer (ie, lubricant) in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. And a step of coating the protective film on the protective film. By using a mixed solvent in which a hydrocarbon solvent and an alcohol solvent are combined, a uniform thin lubricant layer with very little coating unevenness can be formed. Therefore, according to the method for manufacturing a magnetic recording medium of the present invention, it is possible to obtain a magnetic recording medium having excellent lubricating performance and high practical reliability.

  The lubricant of the present invention comprises a combination of a specific fluorine-based diester dicarboxylic acid compound and a specific fluorine-based diester compound and / or a specific fluorine-based monoester compound, preferably a specific fluorine-based amino alcohol compound. Combining. This lubricant combines well with the surface of the object to be lubricated (for example, the carbon film surface of a magnetic recording medium) by this specific compound combination, and has excellent lubrication characteristics in various environments. Demonstrate over time. Therefore, the lubricant of the present invention is useful as a lubricant for various machines, devices or parts.

  The lubricant of the present invention is particularly suitable for constituting a lubricant layer of a magnetic recording medium. A magnetic recording medium having a lubricant layer formed of the lubricant of the present invention exhibits excellent running properties and durability. Specifically, the magnetic recording medium exhibits excellent lubricity under various usage conditions and is used for a long time. However, the lubricity is not lowered and the powder has less property. The magnetic recording medium of the present invention is particularly suitable for use in digital video tape recorders and hard disk drives.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described.
The lubricant of the present invention includes at least one compound selected from the fluorine-based diester dicarboxylic acid compound represented by the general formula (a), the fluorine-based diester compound represented by the general formula (b), and the general formula (c). At least one compound selected from fluorine-based monoester compounds represented by The lubricant of the present invention preferably further contains a fluorinated amino alcohol compound represented by the general formula (d). In addition to these specific compounds, the lubricant of the present invention may contain other known lubricants, rust preventives and the like as necessary.

The compound represented by the following general formula (a) has two carboxyl groups, two ester bonds, a terminal group consisting of one alkyl group or alkenyl group, one fluoroether or It has a fluoropolyether chain.

In formula ^(a), R ^1, R ^2, R 3, ^{R 4} each represent hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group, at least one hydrogen of ^{R 1} and ^{R 2, R 3} and At least one of R ⁴ is hydrogen. Accordingly, in the compound represented by the general formula (a), i) R ¹ is hydrogen, R ² is an aliphatic alkyl group or an aliphatic alkenyl group, and R ³ is an aliphatic alkyl group or an aliphatic alkenyl group. A compound in which R ⁴ is hydrogen, ii) R ¹ is an aliphatic alkyl group or an aliphatic alkenyl group, R ² is hydrogen, R ³ is hydrogen and R ⁴ is an aliphatic alkyl group or A compound that is an aliphatic alkenyl group, iii) R ¹ is an aliphatic alkyl group or an aliphatic alkenyl group, R ² is hydrogen, R ³ is an aliphatic alkyl group or an aliphatic alkenyl group, and R ⁴ is hydrogen, compound, and iv) R ¹ is a hydrogen R ² is an aliphatic alkyl group or an aliphatic alkenyl group, R ⁴ R ³ is a hydrogen in an aliphatic alkyl group or an aliphatic alkenyl group That compound, and ^v) R 1 ^{~R 4} is includes compounds are all hydrogen.

In the general formula (a), the number of carbon atoms of the aliphatic alkyl group or aliphatic alkenyl group (that is, one or more of R ¹ , R ² , R ³ and R ⁴ are aliphatic alkyl groups or aliphatic alkenyl groups). The number of carbon atoms of the group or groups in the case of a group is preferably 1 to 22, more preferably 8 to 18. The aliphatic alkyl group or the aliphatic alkenyl group may be either a straight chain or a branched chain. When a plurality of groups of R ¹ , R ² , R ³ and R ⁴ are an aliphatic alkyl group or an aliphatic alkenyl group, the plurality of groups may be the same group or different from each other. Also good.

  In the general formula (a), m is an integer of 1 to 6, n is an integer of 1 to 5, and p and q are integers of 0 to 30, respectively. m is more preferably an integer of 2 to 5. n is more preferably an integer of 1 to 4. A preferred combination of (m, n) is (2, 1) or (1, 2). p is more preferably an integer of 2 to 6, and q is more preferably an integer of 2 to 6. r is an integer of 1-12.

In the general formula (a), when the moiety represented by — (OC _m F _2m ) _p (OC _n F _2n ) _q — consists of only one kind of oxyfluoroalkylene, q = 0 in the general formula (a) The compound represented by the general formula (a) includes only (OC _m F _2m ). In this case, m is preferably 2.

  When p and q are both 0, the compound represented by the general formula (a) contains one ether bond, and therefore includes a so-called fluoroether. When p ≠ 0 and q = 0, or when p and q are both integers of 1 or more, the number of ether bonds in the compound represented by the general formula (a) is 2 or more, and the compound is a fluoropolyether. Will contain chains.

In formula _{(a) - (OC m F} 2m) p (OC n F 2n) q - moiety represented by the two oxyfluoroalkylene units corresponds to the portion that is copolymerized. p and q represent the number of each oxyfluoroalkylene unit in the copolymer. A copolymer composed of oxyfluoroalkylene units (OC _m F _2m ) and oxyfluoroalkylene units (OC _n F _2n ) is composed of p (OC _m F _2m ) blocks and q (OC _n F _2n ). It may be a block copolymer consisting of these blocks, or another block copolymer, a random copolymer, or an alternating copolymer. Therefore, formula _(a) - include moieties represented by the block copolymer, those which are random copolymers and alternating copolymers _{- (OC m F 2m) p} (OC n F 2n) q.

  The compound represented by the general formula (a) is produced by mixing and stirring an alkyl succinic anhydride, an alkenyl succinic anhydride, or a succinic anhydride and a fluoroalkyl dialcohol having a fluoroalkylene oxide group. Since the method of synthesizing the compound represented by the general formula (a) is known as described in Patent Document 3, for example, detailed description thereof is omitted here.

The compound represented by the following general formula (b) has two ester bonds, a terminal group consisting of two alkyl groups or alkenyl groups, and one fluoroether or fluoropolyether chain in the same molecule.

In the general formula (b), the aliphatic alkyl group or the aliphatic alkenyl group (that is, R ⁵ and R ⁶ preferably have 1 to 30 carbon atoms, more preferably 6 to 20 carbon atoms). When the number of carbon atoms is less than 30, or when the number of carbon atoms exceeds 30, the lubricating performance exhibited by the compound may be reduced, and the aliphatic alkyl group or the aliphatic alkenyl group may be either linear or branched. May

  In general formula (b), x is an integer of 1 to 6, y is an integer of 1 to 5, and s and t are integers of 0 to 30, respectively. x is more preferably an integer of 2 to 5. y is more preferably an integer of 1 to 4. A preferred combination of (x, y) is (2,1) or (1,2). s is more preferably an integer of 2 to 6, and t is more preferably an integer of 2 to 6. u is an integer of 1-12.

In the general formula (b), when the moiety represented by — (OC _x F _2x ) _s (OC _y F _2y ) _t — consists of only one kind of oxyfluoroalkylene, t = 0 in the general formula (b) And the compound represented by the general formula (b) contains only (OC _x F _2x ). In this case, x is preferably 2.

  When both s and t are 0, the compound represented by the general formula (b) includes one ether bond, and thus includes a so-called fluoroether. When s ≠ 0 and t = 0, or when both s and t are integers of 1 or more, the number of ether bonds in the compound represented by the general formula (b) is 2 or more, and the compound is a fluoropolyether. Will contain chains.

In formula _{(b) - (OC x F} 2x) s (OC y F 2y) t - moieties represented by the two oxyfluoroalkylene units corresponds to the portion that is copolymerized. s and t indicate the number of each oxyfluoroalkylene unit in the copolymer. A copolymer composed of oxyfluoroalkylene units (OC _x F _2x ) and oxyfluoroalkylene units (OC _y F _2y ) is composed of s (OC _x F _2x ) blocks and t (OC _y F _2y ). It may be a block copolymer consisting of these blocks, or another block copolymer, a random copolymer, or an alternating copolymer. Therefore, formula (b) - include moieties represented by the block copolymer, those which are random copolymers and alternating copolymers _{- (OC x F 2x) s} (OC y F 2y) t.

When the compound represented by the general formula (b) is used as a component of the lubricant of the present invention,-(OC _m F _2m ) _p (OC _n F _2n ) _{q of the} compound represented by the general formula (a) - the part indicated by the general formula (b) of the compound represented by _{- (OC x F 2x) s} (OC y F 2y) t - moieties represented by is preferably the same. That is, it is preferable that m = x, n = y, p = s, and q = t. In that case, since the basic skeleton of the two components is common, the compatibility of the two components becomes better.

  The method for synthesizing the compound represented by the general formula (b) is produced, for example, by reacting a perfluoropolyether having a hydroxyl group at a terminal with a carboxylic acid chloride. Since the method of synthesizing the compound represented by the general formula (b) is known as described in, for example, Patent Document 4, detailed description thereof is omitted here.

The compound represented by the following general formula (c) has one ester bond, one end group consisting of one alkyl group or alkenyl group, one fluoroalkyl end group, one fluoroether end group, With fluoropolyether end groups.

In the general formula (c), R ⁷ is a fluoroalkyl group, a fluoroether group, or a fluoropolyether group.

When R ⁷ is a fluoroalkyl group or a fluoroalkenyl group, the carbon number thereof is preferably 1 to 12, and more preferably 6 to 10. The fluoroalkyl group or fluoroalkenyl group may be either a straight chain or a branched chain. The fluoroalkyl group or fluoroalkenyl group is preferably a perfluoroalkyl group or a perfluoroalkenyl group.

When R ⁷ is a fluoroalkyl group or a fluoroalkenyl group, R ⁷ may have a fluorinated cyclic hydrocarbon group. The fluorinated cyclic hydrocarbon group is a substituent selected from an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and a condensed polycyclic hydrocarbon group in which part or all of hydrogen is substituted with fluorine. And preferably an alicyclic hydrocarbon group (that is, a cycloalkyl group). In the fluorinated cyclic hydrocarbon group, it is preferable that all hydrogens are substituted with fluorine. The cyclic hydrocarbon group substitutes hydrogen or fluorine of the fluoroalkyl group or fluoroalkenyl group. The cyclic hydrocarbon group may be bonded to any carbon of the fluoroalkyl group or the fluoroalkenyl group, for example, may be bonded as a side chain group. The cyclic hydrocarbon group is preferably bonded to the terminal carbon of the fluoroalkyl group or fluoroalkenyl group. The carbon number of the fluorinated cyclic hydrocarbon group is preferably 4-8.

When R ⁷ is a fluoroether group or a fluoropolyether group, the molecular weight is preferably about 200 to about 6000, more preferably about 300 to about 4000. When the molecular weight is less than 200 or exceeds 6000, the lubricity and reliability of the magnetic recording medium may be lowered when the lubricant layer of the magnetic recording medium is formed with a lubricant containing this compound. The fluoroether group or fluoropolyether group is preferably a perfluoroether group or a perfluoropolyether group.

In the general formula (c), R ⁸ is an aliphatic alkyl group or an aliphatic alkenyl group. R ⁸ preferably has 6 to 30 carbon atoms, and more preferably 10 to 24 carbon atoms. When the number of carbon atoms is less than 6 or more than 30, the lubrication performance may be deteriorated. R ⁸ may be linear or branched.

  The compound represented by the general formula (c) can be synthesized by reacting a fluorinated alcohol and a fatty acid. This reaction can be conveniently carried out by mixing and stirring the fluorinated alcohol and the fatty acid while heating in a solvent in the presence of a catalyst. It is preferable to use heptane, octane or toluene as the solvent. Further, when the heating temperature is low, a large amount of unreacted material tends to remain, and when the heating temperature is high, a by-product tends to be generated. Therefore, the heating temperature is preferably 80 to 150 ° C, more preferably 120 to 130 ° C. As the catalyst, an acid catalyst or a base catalyst can be used. A preferable example of the acid catalyst is p-toluenesulfonic acid. A preferable base catalyst is, for example, pyridine. It is also possible to use fatty acid chloride in place of the fatty acid. In this case, there is no need for a catalyst.

  The lubricant of the present invention comprises a compound represented by the general formula (a) and a compound represented by the general formula (b) and / or the general formula (c) in a weight ratio of 1: 9 to 9: 1. More preferably in a ratio of 2: 8 to 9: 1, and still more preferably in a ratio of 4: 6 to 9: 1. When the lubricant includes both the compound represented by the general formula (b) and the compound represented by the general formula (c) (that is, a three-component lubricant), the ratio between the former and the latter is expressed by weight ratio. It is preferably 1: 9 to 9: 1.

  The lubricant of the present invention further contains a compound represented by the following general formula (d). That is, the lubricant of the present invention is obtained by simplifying the compounds represented by the general formulas and displaying (a), (b), (c), and (d) when (a) / (b) / It is preferably provided as a three-component system (d) or (a) / (c) / (d) or a four-component system (a) / (b) / (c) / (d).

  The compound represented by the general formula (d) contains two nitrogen atoms and two hydroxyalkyl groups in the molecule, preferably at least one, and more preferably two aliphatic alkyl groups or aliphatic alkenyl groups. .

In the general formula (d), R ⁹ and R ¹⁰ each represent hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group, b is an integer of 1 to 12, v is an integer of 1 to 12, and w is It is an integer of 1-6, z is an integer of 1-5, h and k are integers of 0-30, respectively.

R ⁹ and R ¹⁰ are generally the same but may be different from each other. When R ⁹ and R ¹⁰ are different from each other, one may be hydrogen. Alternatively, R ⁹ and R ¹⁰ may both be hydrogen. The compound of R ⁹ = R ¹⁰ = H is slightly inferior in terms of lubricity compared to the compound in which R ⁹ and / or R ¹⁰ is an aliphatic alkyl group or an aliphatic alkenyl group. Therefore, it is preferably used as a compound constituting the lubricant of the present invention.

In the general formula (d), the aliphatic alkyl group or the aliphatic alkenyl group (that is, R ⁹ and / or R ¹⁰ preferably has 1 to 30 carbon atoms, more preferably 6 to 20 carbon atoms). When the number of carbon atoms is less than 6 or the number of carbon atoms exceeds 30, the lubricating performance exhibited by the compound may be reduced.The aliphatic alkyl group or the aliphatic alkenyl group may be either linear or branched. It may be.

  In general formula (d), w is an integer of 1 to 6, z is an integer of 1 to 5, and h and k are integers of 0 to 30, respectively. More preferably, w is an integer of 2-5. z is more preferably an integer of 1 to 4. A preferred combination of (w, z) is (2,1) or (1,2). h is more preferably an integer of 2 to 6, and k is more preferably an integer of 2 to 6. b is an integer of 1 to 12, and v is an integer of 1 to 12.

In the general formula (d), when the moiety _represented by — (OC _w F _2w ) _h (OC _z F _2z ) _k — consists of only one oxyfluoroalkylene, k = 0 in the general formula (a). And the compound represented by the general formula (d) includes only (OC _w F _2w ). In this case, w is preferably 2.

  When both h and k are 0, the compound represented by the general formula (d) contains one ether bond, and thus includes a so-called fluoroether. When h ≠ 0 and k = 0, or when both h and k are integers of 1 or more, the number of ether bonds in the compound represented by the general formula (d) is 2 or more, and the compound is a fluoropolyether. Will contain chains.

In the general formula (d), the moiety represented by — (OC _w F _2w ) _h (OC _z F _2z ) _k — corresponds to a moiety in which two kinds of oxyfluoroalkylene units are copolymerized. h and k represent the number of each oxyfluoroalkylene unit in the copolymer. A copolymer composed of oxyfluoroalkylene units (OC _w F _2w ) and oxyfluoroalkylene units (OC _z F _2z ) is composed of h (OC _w F _2w ) blocks and k (OC _z F _2z ). It may be a block copolymer consisting of these blocks, or another block copolymer, a random copolymer, or an alternating copolymer. Accordingly, the general formula (d) includes those in which the moiety represented by — (OC _w F _2w ) _h (OC _z F _2z ) _k — is a block copolymer, a random copolymer, or an alternating copolymer.

The compound represented by the general formula (d) can be obtained by the synthesis method shown below. First, a carboxylic acid-modified fluoroalkyl ether compound is reacted with thionyl chloride to obtain a dicarboxylic acid chloride. Next, the dicarboxylic acid chloride is reacted with an alkanolamine having an aliphatic hydrocarbon chain to obtain an amide-modified fluoroalkyl ether compound. Next, the fluoroalkyl polyether compound of the present invention is obtained by reducing the amide-modified product with a catalyst such as LiAlH ₄ (lithium aluminum hydride). As the catalyst, for example, NaBH ₄ or Bu ₃ SnH can be used in addition to LiAlH ₄ .

When the compound represented by the general formula (d) is used as a component of the lubricant of the present invention, — (OC _m F _2m ) _p (OC _n F _2n ) _{q of the} compound represented by the general formula (a) - a part indicated by, the general formula (d) compound represented by _{- (OC w F 2w) h} (OC z F 2z) k - moieties represented by is preferably the same. That is, it is preferable that m = w, n = z, p = h, and q = k. In that case, since the basic skeletons of the two components are common, the compatibility of the two components becomes better. Similarly, when the compound represented by the general formula (a), the compound represented by the general formula (b), and the compound represented by the general formula (d) are combined, the compound represented by the general formula (a) -(OC _m F _2m ) _p (OC _n F _2n ) _q- and-(OC _x F _2x ) _s (OC _y F _2y ) _{t-of the} compound represented by the general formula (b) a moiety represented by the general formula (d) at the indicated by the compound _{- (OC w F 2w) h} (OC z F 2z) k - moieties represented by is preferably the same. That is, it is preferable that m = x = w, n = y = z, p = s = h, and q = t = k. In that case, since the basic skeleton of the three components is common, the compatibility of the three components becomes better.

  The lubricant of the present invention comprises a fluorine-based diester dicarboxylic acid compound represented by the general formula (a), a fluorine-based diester compound represented by the general formula (b) and / or a fluorine represented by the general formula (c). When a monoester compound and a fluorine-based amino alcohol compound represented by the general formula (d) are included, the fluorine-based diester dicarboxylic acid compound represented by the general formula (a) and other 2 or 3 compounds ( That is, the mixing ratio of (b) + (d), or (c) + (d), or (b) + (c) + (d)) ranges from 1: 9 to 9: 1 in weight ratio. Preferably in the range of 2: 8 to 9: 1, more preferably in the range of 4: 6 to 9: 1. In such a lubricant, a fluorine-based diester compound represented by the general formula (b) and / or a fluorine-based monoester compound represented by the general formula (c), and a fluorine-based amino alcohol compound represented by the general formula (d) Is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 2: 8 to 8: 2, and in the range of 4: 6 to 6: 4. Even more preferably. Further, when such a lubricant contains all of the compound represented by the general formula (b), the compound represented by the general formula (c), and the compound represented by the general formula (d), the mixing ratio thereof is It is preferably 1: 1: 18 to 9: 9: 2 ((b) :( c) :( d)).

  As described above, the lubricant of the present invention may contain other lubricants, rust preventives and / or extreme pressure agents in addition to the compounds represented by the general formulas (a) to (d). In that case, a compound represented by the general formula (a), a compound represented by the general formula (b) and / or a compound represented by the general formula (c) and optionally a compound represented by the general formula (d) The total amount is preferably 30% by weight or more, more preferably 50% by weight or more of the total amount of them combined with other lubricants and the like. A combined amount of the compound represented by the general formula (a), the compound represented by the general formula (b) and / or the compound represented by the general formula (c), and the compound represented by the general formula (d) which is optionally contained. If it is less than 30% by weight, for example, when a lubricant layer of a magnetic recording medium is formed with this composition, good lubricating properties may not be imparted to the magnetic recording medium.

The magnetic recording medium of the present invention has a ferromagnetic metal film formed as a magnetic layer on a nonmagnetic support, a protective film formed on the magnetic layer, and a lubricant layer formed on the protective film. In the magnetic recording medium, the lubricant layer contains the lubricant of the present invention. The amount of the lubricant of the present invention contained in the lubricant layer is preferably 0.05 to 100 mg, more preferably 0.1 to 50 mg per 1 m ² of the surface of the lubricant layer. In order to make such a small amount of lubricant uniformly exist in the lubricant layer, it is desirable to form the lubricant layer of the magnetic recording medium of the present invention by the following method.

  The lubricant layer is formed on the protective film after forming a ferromagnetic metal film and a protective film in this order on the nonmagnetic support using conventional materials and means. The step of forming the lubricant layer includes a step of applying a coating solution prepared by dissolving the lubricant of the present invention in a mixed solvent of a hydrocarbon solvent and an alcohol solvent on the protective film, and drying the applied coating solution. And evaporating the mixed solvent. Finally, when the mixed solvent evaporates, the lubricant dissolved in the solvent remains on the protective film to form a lubricant layer. Therefore, even if the coating solution is applied thickly, the solvent evaporates to form a uniform and very thin lubricant layer on the protective film, that is, a lubricant layer with a small amount of lubricant uniformly covering the protective film. Is done.

  Examples of the hydrocarbon solvent that can be used in the present invention include toluene, hexane, heptane, octane, nonane, xylene, and ketone. Examples of alcohol solvents that can be used in the present invention are lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Specifically, the mixed organic solvent is preferably a mixed solvent of toluene and isopropyl alcohol, a mixed solvent of hexane and isopropyl alcohol, or a mixed solvent of heptane and isopropyl alcohol. If the proportion of the alcohol solvent is too large, coating unevenness is likely to occur. On the other hand, if the proportion of the hydrocarbon solvent is too large, it is disadvantageous in terms of cost. It is preferable to use the mixture so as to be in the range of 1, preferably in the range of 3: 7 to 7: 3.

  The concentration of the coating solution and the coating thickness are applied so that the lubricant layer formed on the protective film after the solvent evaporates has a desired thickness. Generally, it is preferable to apply a coating solution having a lubricant concentration of 100 to 10000 ppm so as to have a thickness of 10 to 100 μm.

  As a method of forming a lubricant layer using the above mixed solvent, wet coating methods such as bar coating method, gravure coating method, reverse roll coating method, die coating method, dip coating method, and spin coating method, or organic vapor deposition methods may be used. Yes, either method may be adopted.

  After applying the coating solution, the lubricant layer is formed on the protective film by drying and evaporating the organic solvent. The drying process can be performed by heating or natural drying. The thickness of the finally obtained lubricant layer is preferably about 3 to 5 nm. However, since there is an optimum range of the thickness of the lubricant layer depending on the composition of the lubricant, the thickness of the lubricant layer is not necessarily limited to this range.

  In this way, by using a predetermined mixed organic solvent, a uniform thickness lubricant layer without application unevenness is obtained, and after the solvent has finally evaporated, a very thin lubricant layer of several nm is formed. Can be formed. As a result, a magnetic recording medium having excellent lubrication performance and high practical reliability can be obtained.

  As described above, the magnetic recording medium of the present invention can be formed using conventional materials and means for the layers other than the lubricant layer.

  For example, the nonmagnetic support is a film made of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide, or aromatic polyimide; a film made of vinyl resin such as polyvinyl chloride or polyvinylidene chloride; polycarbonate, glass, ceramic, carbon A substrate made of a metal such as aluminum or copper, a light metal such as an aluminum alloy or a titanium alloy, or single crystal silicon; or paper. When using a rigid substrate such as an aluminum alloy substrate or glass substrate as the non-magnetic support, an oxide film or Ni-P film is formed on the substrate surface by anodizing to harden the surface. May be.

The surface of the non-magnetic support on which the ferromagnetic metal film is formed (that is, the surface that is in direct contact with the magnetic layer or in some cases through the underlayer, etc.) has practical reliability and good RF output value. In order to achieve both, it is desirable that a protrusion forming process having a diameter of 20 to 700 nm and a height of 5 to 70 nm is performed. Specifically, for example, the protrusions are formed by dispersing and fixing ultrafine particles made of an inorganic material such as SiO ₂ or ZnO or ultrafine particles made of an organic material such as imide on the surface of the nonmagnetic support. . Alternatively, the protrusions are formed by forming a polymer material containing such fine particles into a film.

  In the magnetic recording medium of the present invention, the magnetic layer is a ferromagnetic metal film. Ferromagnetic metals suitable for the magnetic layer include Fe-based metals, Co-based metals, and Ni-based metals. In the present invention, it is particularly preferable to form the magnetic layer with a Co-based metal. Here, “Co-based metal” refers to cobalt and an alloy containing cobalt as a main component and preferably 50 atomic% or more. The same applies to “Fe-based metal” and “Ni-based metal”.

  Specifically, the ferromagnetic metal film includes Fe, Co and Ni, and Co—Ni, Co—Fe, Co—Cr, Co—Cu, Co—Pt, Co—Pd, Co—Sn, Co—Au, Selected from alloys such as Fe-Cr, Fe-Co-Ni, Fe-Cu, Ni-Cr, Fe-Co-Cr, Co-Ni-Cr, Co-Pt-Cr and Fe-Co-Ni-Cr It is made of one or more materials. The ferromagnetic metal film may contain oxygen, which may be contained in the form of oxides of these metals or alloys. The ferromagnetic metal film may be in the form of a single layer film or in the form of a multilayer film.

  The ferromagnetic metal film can be formed by an ion plating method, a sputtering method, an electron beam evaporation method, or the like. If the ferromagnetic metal film is formed in an oxygen atmosphere, oxygen is contained in the ferromagnetic metal film. The thickness of the ferromagnetic metal film is generally 30 nm to 300 nm.

The protective film is preferably a carbon film. The carbon film has a high Vickers hardness of about 2.45 × 10 ⁴ N / mm ² (about 2500 kg / mm ² ) and prevents damage to the magnetic recording medium together with the lubricant layer. Considering the balance between practical reliability and output, the thickness is preferably 1 to 20 nm.

  The carbon film is preferably graphitic carbon or diamond-like carbon. Diamond-like carbon is the most preferable material because it has an appropriate hardness and can suppress damage to the magnetic recording medium without damaging the magnetic head. A carbon film made of graphite-like carbon or diamond-like carbon is formed by a plasma CVD method using only a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas, or by a sputtering method using a carbon target. It is formed.

  Specifically, the carbon film is vacuumed in a state where a hydrocarbon gas or a mixed gas of hydrocarbon gas and an inert gas such as argon is introduced into a vacuum vessel, and the pressure in the vessel is maintained at 0.13 to 130 Pa. It is formed on the ferromagnetic metal film by generating a discharge inside the container and generating a plasma of hydrocarbon gas. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be determined experimentally. In addition, by applying a voltage of 0 kV to -3 kV to the electrode disposed on the nonmagnetic support side, the hardness of the carbon film can be increased, and the adhesion between the carbon film and the ferromagnetic metal film is improved. Can be made. As the hydrocarbon gas, methane, ethane, propane, butane, pentane, hexane, heptane, octane, benzene, or the like can be used.

  In order to form a hard carbon film, it is desirable to increase the discharge energy, and it is also desirable to maintain the temperature of the nonmagnetic support at a high temperature. For example, it is desirable that the discharge energy has an effective value of 600 V or more by superimposing an alternating current, for example, a high frequency current and a direct current.

  In the present invention, it is preferable that a nitrogen-containing plasma polymerized film is formed on the surface portion of the carbon film, and the lubricant layer is formed on the nitrogen-containing plasma polymerized film of the carbon film. Nitrogen-containing plasma polymerization results in the presence of amino groups in the surface layer of the carbon film, resulting in greater adhesion strength between the lubricant layer and the carbon film, and further improving the durability of the magnetic recording medium. It becomes. Combined with the inclusion of a specific fluoroalkyl ether compound in the lubricant layer, the running durability, the still durability and the corrosion resistance are improved with excellent lubrication performance without impairing the electromagnetic conversion characteristics. A highly reliable magnetic recording medium can be obtained.

  The nitrogen-containing plasma polymerized film is obtained by gasifying and introducing an amine compound such as propylamine, butylamine, ethylenediamine, propylenediamine or tetramethylenediamine into a vacuum vessel, and maintaining the pressure in the vessel at 0.13 to 130 Pa. The high frequency discharge is generated inside the vacuum vessel. By forming the nitrogen-containing plasma polymerized film, the chemical adsorption force of the lubricant containing the specific fluorine-containing compound is improved, and as a result, the adhesion strength between the lubricant layer and the carbon film is improved. The film thickness of the nitrogen-containing plasma polymerized film is suitably less than 3 nm. If the nitrogen-containing plasma polymerized film is thicker than this, the protective effect of the carbon film is lowered. Incidentally, methods for forming a nitrogen-containing plasma polymerized film on the surface layer of the carbon film are disclosed in US Pat. Nos. 5,540,957 and 5,637,393, and the contents disclosed in these patents by this reference are described in this specification. Part of it.

  The magnetic recording medium of the present invention may have a backcoat layer on the surface opposite to the surface on which the magnetic layer of the nonmagnetic support is formed. The backcoat layer may be a layer formed of one or more materials selected from polyurethane, nitrocellulose, polyester, carbon, calcium carbonate, etc., or a thin film made of metal, metal oxide, or alloy. It's okay. The thickness of the backcoat layer is preferably about 50 to 500 nm.

  The magnetic recording medium of the present invention is not limited to the above configuration. For example, the magnetic recording medium of the present invention has a reinforcing layer formed by vapor deposition of metal on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed, and the backcoat layer is formed on the reinforcing layer. It may be of a formed configuration. Alternatively, the magnetic recording medium of the present invention has a configuration in which a nonmagnetic support has a reinforcing layer on the surface subjected to the protrusion treatment and the magnetic layer is formed on the reinforcing layer, or on the reinforcing layer. The underlayer and the magnetic layer may be stacked in this order. The magnetic recording medium of the present invention may be in the form of a tape or a disk.

  FIG. 1 is a sectional view schematically showing an example of the magnetic recording medium of the present invention. In FIG. 1, a magnetic layer (2) is formed on one surface of a nonmagnetic support (1), a protective film (3) is formed on the magnetic layer, and a lubricant is formed on the protective film (3). A magnetic recording medium (100) is shown in which a layer (4) is formed and a backcoat layer (5) is formed on the other surface of the nonmagnetic support (1).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this Example.

(Example 1)
In Example 1, an example of the magnetic recording medium and the method of manufacturing the magnetic recording medium of the present invention will be described.
As a nonmagnetic support, a polyester film having granular protrusions on the surface was prepared. Specifically, (1) having a plurality of gently-gradient protrusions (average height 7 nm, diameter 1 μm) per 100 μm ² formed by forming a polymer material containing silica fine particles into a film, and ( 2) colloidal silica particles having a diameter of 15nm was used a polyester film having ² per 1 × 10 ⁷ cells 1mm steep projections formed is fixed to the polyester film surface with ultraviolet curable epoxy resin. The polyester film used in this example had a very small number of relatively large protrusions formed on the film surface by fine particles derived from the residue of the polymerization catalyst.

  A ferromagnetic metal film (thickness: 100 nm) made of Co was formed on the surface of the polyester film on which the granular protrusions were formed by continuous vacuum oblique deposition in the presence of a small amount of oxygen. The oxygen content in the ferromagnetic metal film was 5% in atomic fraction.

  Next, a protective film having a thickness of 5 nm made of diamond-like carbon was formed on the ferromagnetic metal film by plasma CVD. The protective film introduces a gas in which hexane gas and argon gas are mixed at a ratio of 4: 1 (pressure ratio) into a vacuum vessel, and keeps the total gas pressure at 39 Pa, while the frequency is 20 kHz, the voltage is 1500 V AC and 1000 V. The direct current was superimposed and applied to the electrode in the discharge tube. Further, propylamine gas is introduced onto the carbon film, and a high frequency plasma treatment of 10 kHz is performed while maintaining a pressure of 6.5 Pa to form a nitrogen-containing plasma polymerization film having a thickness of 2.5 nm on the surface layer of the carbon film. did.

Subsequently, a lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based diester compound represented by the chemical formula (b1) at a ratio of 1: 1 (weight ratio). This lubricant was dissolved in a mixed organic solvent (weight ratio 1: 1) of isopropyl alcohol and toluene to prepare a coating solution.

The prepared coating solution was applied onto the protective film by a wet coating method using a reverse roll coater, and then dried to evaporate the solvent. Finally, a lubricant layer containing 7 mg of lubricant per 1 m ² of the surface was formed on the protective film. This was cut into a predetermined width to produce a magnetic tape.

(Example 2)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based diester compound represented by the chemical formula (b1) at a ratio of 7: 3 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 3)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a2) and the fluorine-based diester compound represented by the chemical formula (b2) at a ratio of 4: 6 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

Example 4
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a3) and the fluorine-based diester compound represented by the chemical formula (b2) at a ratio of 1: 1 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 5)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a3) and the fluorine-based diester compound represented by the following chemical formula (b3) at a ratio of 1: 1 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 6)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based monoester compound represented by the following chemical formula (c1) at a ratio of 1: 1 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 7)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based monoester compound represented by the following chemical formula (c2) at a ratio of 1: 1 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 8)
The fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1), the fluorine-based diester compound represented by the chemical formula (b1), and the fluorine-based monoester compound represented by the chemical formula (c1) are 1: 1: 1. A lubricant was prepared by mixing at a ratio of (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

Example 9
1: 1: 1 a fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1), a fluorine-based diester compound represented by the chemical formula (b1), and a fluorine-based amino alcohol compound represented by the following chemical formula (d1) A lubricant was prepared by mixing at a ratio of (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 10)
A fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1), a fluorine-based monoester compound represented by the chemical formula (c1), and a fluorine-based amino alcohol compound represented by the chemical formula (d1) are 1: 1: A lubricant was prepared by mixing at a ratio of 1 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Example 11)
A fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1), a fluorine-based diester compound represented by the chemical formula (b1), a fluorine-based monoester compound represented by the chemical formula (c1), and the chemical formula (d1). Was mixed with the fluorine-based aminoalcohol compound represented by the formula (1: 1: 1: 1 (weight ratio)) to prepare a lubricant. Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Comparative Example 1)
A magnetic tape was produced in the same manner as in Example 1 using only the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) as a lubricant.

(Comparative Example 2)
A magnetic tape was produced in the same manner as in Example 1 using only the fluorine-based diester compound represented by the chemical formula (b1) as a lubricant.

(Comparative Example 3)
A magnetic tape was produced in the same manner as in Example 1 using only a known compound represented by the following chemical formula (e1) as a lubricant.

(Comparative Example 4)
A magnetic tape was produced in the same manner as in Example 1 using only the fluorine-based amino alcohol compound represented by the chemical formula (d1).

(Comparative Example 5)
A magnetic tape was produced in the same manner as in Example 1 using a compound which is a known lubricant represented by the following chemical formula (z1).

(Comparative Example 6)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based monoester compound represented by the chemical formula (e1) at a ratio of 1: 1 (weight ratio). Using this lubricant, a magnetic tape was produced in the same manner as in Example 1.

(Comparative Example 7)
A magnetic tape was produced in the same manner as in Example 1 using only the fluorine monoester compound represented by the chemical formula (c1) as a lubricant.

(Comparative Example 8)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based diester compound represented by the chemical formula (b1) at a ratio of 1: 1 (weight ratio). A magnetic tape was produced in the same manner as in Example 1 except that this lubricant was dissolved in isopropyl alcohol (single solvent) to prepare a coating solution.

(Comparative Example 9)
A lubricant was prepared by mixing the fluorine-based diester dicarboxylic acid compound represented by the chemical formula (a1) and the fluorine-based diester compound represented by the chemical formula (b1) at a ratio of 1: 1 (weight ratio). A magnetic tape was produced in the same manner as in Example 1 except that this lubricant was dissolved in toluene (single solvent) to prepare a coating solution.

  The magnetic tape samples obtained in Examples 1 to 11 and Comparative Examples 1 to 9 were evaluated as follows.

(I) Running test Each sample was wound around a friction member (made of stainless steel (SUS420J2, surface roughness 0.2S), outer diameter 6 mm) at a winding angle of 90 ° in an environment of 23 ° C. and 50% RH, and tension 0 The sample was unwound at a speed of 18 mm / sec under the condition of 2N, wound at the same speed, and the tension was measured on the winding side. The dynamic friction coefficient was calculated from the ratio of the tension on the winding side and the tension on the winding side using the Euler equation. One unwinding and one winding were set as one pass, and the friction coefficient at the 100th pass and the 1000th pass was calculated for each sample.

(II) Still life test Still life was measured in a 3 ° C, 5% RH environment using a commercially available digital VTR (made by Matsushita Electric Industrial Co., Ltd., trade name NV-DJ1) modified for still life measurement. . The still life is indicated by the time (minutes) from the beginning until the output drops by 6 dB.

(III) Durability test Durability was evaluated by clogging the head. Using a commercially available digital VTR (NV-DJ1 manufactured by Matsushita Electric Industrial Co., Ltd.) modified for RF (high frequency) output measurement, each sample was repeatedly reproduced for 1330 hours in an environment of 23 ° C. and 60% RH. The head clogging was measured from the RF output during reproduction. During this repeated reproduction, head clogging occurred when the RF output decreased by 6 dB or more, and the total time for which such reduction was measured was defined as head clogging.

Further, the magnetic head after repeated reproduction was observed using an optical microscope, and the dust attached to the magnetic head was observed. Evaluate powder with 5 levels, 5 is the level at which almost no powder is seen, 4 is the level when powder is less than 30% of the head area and does not affect the output, and the level with powder is less than 50% of the head area The level at which the output does not affect the output is 3, the level at which the dust is 50% or less of the head area and the level at which the output is affected is 2, and the level at which the powder is 50% or more the head area is 1.
The evaluation results of each test are shown in Table 1.

(IV) Adsorption test The adsorption test was performed by immersing the sample in which the lubricant layer was formed by immersing the sample in the solvent used for preparing the coating liquid when forming the lubricant layer for 10 seconds. The residual ratio of the lubricant was determined. According to this test, the larger the residual ratio, the higher the adsorptivity is evaluated. The residual rate of the lubricant was determined from the amount of change in the amount of fluorine atoms before and after washing with a solvent by detecting fluorine atoms by ESCA analysis.
The evaluation results of each test are shown in Table 1.

  As is apparent from Table 1, the samples of Examples 1 to 11 using a lubricant comprising a combination of a specific fluorine-based dicarboxylic acid diester compound and a specific fluorine-based diester compound or a specific fluorine-based monoester compound are In an environment such as normal temperature and normal humidity and low temperature and low humidity, it showed excellent running durability and durability, and long still life. Specifically, the magnetic tapes of Examples 1 to 11 maintained a low coefficient of friction even after running for 1000 passes, and the still life was longer than 90 minutes. Using a lubricant comprising only the compound represented by the general formula (a), only the compound represented by the general formula (b), the compound represented by the general formula (c), and the compound represented by the general formula (d) The produced magnetic tapes of Comparative Examples 1, 2, 7, and 4 were all inferior in terms of runnability, still life, and durability. Moreover, the magnetic tapes of Comparative Example 3 and Comparative Example 5 produced using a known lubricant were also inferior in terms of runnability, still life, and durability. The magnetic tape of Comparative Example 6 produced using a lubricant obtained by mixing a compound represented by the general formula (a) and an ester other than the esters represented by the general formulas (b) and (c) It was inferior to those of Examples 1 to 11 in terms of durability. From these results, a combination of the compound represented by the general formula (a) and the compound represented by the general formula (b) or the general formula (c), and a compound represented by the general formula (d) in this combination. It can be seen that the combination functions extremely well as a lubricant for magnetic recording media. In particular, it can be seen that the combination of the compound represented by the general formula (a) and the compound represented by the general formula (d) has a high lubricant residual ratio and is excellent in terms of the adsorption characteristics of the lubricant. Further, based on the results of Example 1 and Comparative Examples 8 and 9, the lubricant of the present invention was dissolved in a mixed solvent of a hydrocarbon solvent and an alcohol solvent and applied, whereby a lubricant having good characteristics. It can be seen that a layer can be formed.

  The lubricant of the present invention is a combination of two or more specific compounds so that the effects brought about by each of them are exhibited synergistically. The lubricant of the present invention is particularly suitable for constituting a lubricant layer of a magnetic recording medium. For example, the lubricant layer of a magnetic recording medium used in a digital video tape recorder, a hard disk drive, etc. Suitable for constructing a lubricant layer to be rubbed with.

Schematic sectional view of an example of the magnetic recording medium of the present invention

Explanation of symbols

1 Nonmagnetic support 2 Magnetic layer (ferromagnetic metal thin film)
3 Protective film 4 Lubricant layer 5 Backcoat layer 100 Magnetic recording medium

Claims (13)

At least one compound selected from fluorine-based diester dicarboxylic acid compounds represented by the following general formula (a), a fluorine-based diester compound represented by the following general formula (b), and a fluorine-based monoester represented by the following general formula (c) A lubricant comprising at least one compound selected from ester compounds.

^(Wherein, R ^1, R ^2, R 3, ^{R 4} each represent hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group, at least one of ^{R 1} and ^{R 2} are hydrogen, ^{R 3} and ^{R 4} At least one is hydrogen, m is an integer from 1 to 6, n is an integer from 1 to 5, p and q are each an integer from 0 to 30, and r is an integer from 1 to 12. )

(In the formula, R ⁵ and R ⁶ each represent an aliphatic alkyl group or an aliphatic alkenyl group, x is an integer of 1 to 6, y is an integer of 1 to 5, and s and t are each 0. To an integer from 30 to u, and u is an integer from 1 to 12.)

(In the formula, R ⁷ represents a fluoroalkyl group, a fluoroalkenyl group, a fluoroether group or a fluoropolyether group, R ⁸ represents an aliphatic alkyl group or an aliphatic alkenyl group, and a is an integer of 1 to 12. .)   A compound comprising at least one compound selected from the fluorine-based diester dicarboxylic acid compounds represented by the general formula (a) and at least one compound selected from the fluorine-based diester compounds represented by the general formula (b). The lubricant according to 1.   Claims comprising at least one compound selected from fluorine-based diester dicarboxylic acid compounds represented by the general formula (a) and at least one compound selected from fluorine-based monoester compounds represented by the general formula (c). Item 4. The lubricant according to Item 1.   Mixing of the fluorinated diester dicarboxylic acid compound represented by the general formula (a) with the fluorinated diester compound represented by the general formula (b) and / or the fluorinated monoester compound represented by the general formula (c) The ratio according to any one of claims 1 to 3, wherein the ratio is in a range of 1: 9 to 9: 1 by weight ratio. The lubricant according to any one of claims 1 to 4, further comprising a fluorine-based amino alcohol compound represented by the following general formula (d).

(In formula, R <^9> , R < ¹⁰ > shows hydrogen, an aliphatic alkyl group, or an aliphatic alkenyl group, respectively, b is an integer of 1-12, v is an integer of 1-12, w is 1-6. Z is an integer of 1 to 5, and h and k are each an integer of 0 to 30.)   The fluorine-based diester dicarboxylic acid compound represented by the general formula (a), the fluorine-based diester compound represented by the general formula (b) and / or the fluorine-based monoester compound represented by the general formula (c), and the above general The lubricant according to claim 5, wherein the mixing ratio with the fluorine-based amino alcohol compound represented by the formula (d) is in the range of 1: 9 to 9: 1 by weight.   The mixing ratio of the fluorine-type diester compound shown by the said general formula (b) and / or the fluorine-type monoester compound shown by the said general formula (c), and the fluorine-type amino alcohol compound shown by the said general formula (d). Is in the range of 1: 9 to 9: 1 by weight.   A magnetic recording medium lubricant comprising the lubricant according to claim 1.   A magnetic recording medium having a ferromagnetic metal film formed as a magnetic layer on a nonmagnetic support, a protective film formed on the magnetic layer, and a lubricant layer formed on the protective film A magnetic recording medium in which the agent layer contains at least one lubricant according to any one of claims 1 to 7.   The magnetic recording medium according to claim 9, wherein the protective film is diamond-like carbon.   The magnetic recording medium according to claim 9 or 10, wherein the protective film is a carbon film having a nitrogen-containing plasma polymerized film on a surface layer portion, and the lubricant layer is formed on the nitrogen-containing plasma polymerized film of the carbon film. .   12. The method of manufacturing a magnetic recording medium according to claim 9, wherein the step of forming a lubricant layer on the protective film is a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. A method for producing a magnetic recording medium, comprising: applying a coating solution prepared by dissolving a lubricant on a protective film. The method for producing a magnetic recording medium according to claim 12, wherein the mixing ratio of the hydrocarbon solvent and the alcohol solvent is in the range of 1: 9 to 9: 1 by weight.

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